Additional Study Information: The purpose of this study is to compare any good and bad effects of avoiding the hippocampus during whole brain radiation to the usual whole-brain radiation. The hippocampus is part of the brain that is important for memory. Avoiding the hippocampus during whole-brain radiation could decrease the chance of side effects on memory and thinking. It also is possible that avoiding the hippocampus could have no benefit or could cause other side effects. Hippocampal avoidance also could lessen the effectiveness of whole-brain radiation. This study will allow the researchers to know whether this different approach is better, the same, or worse than the usual approach. To be better, the addition of the hippocampal avoidance technique to whole-brain radiation therapy should decrease the chance of side effects on memory or thinking by at least 14.5%. The first portion of this study will test if avoiding the hippocampus during whole-brain radiation is as effective as the usual treatment, whole-brain radiation, in decreasing the chance of cancer spreading to the brain. The second portion of the study will test if hippocampal avoidance decreases memory and thinking side effects.